Hardening of gelatin

ABSTRACT

THIS APPLICATION DESCRIBES A PROCESS FOR THE HARDENING OF GELATIN LAYERS IN PHOTOGRAPHIC MATERIALS DURING THE PROCESSING THEREOF WHICH COMPRISES APPLYING TO THE MATERIAL PRIOR TO OR DURING DEVELOPMENT THEREOF A DIALDEHYE OF THE FOLLOWING GENERAL FORMULA:   1,3-(O=CH-),2-R1,4-R3,5-R2,6-R4-BENZENE   WHEREIN EITHER R1 OR R2 IS AN HYDROXY GROUP, THE OTHER BEING A HYDROGEN OR HALOGEN ATOM OR AN ALKY, ARALKYL, ARYL OR ALKOXY GROUP, R3 AND R4 ARE THE SAME OR DIFFERENT AND ARE A HYDROGEN OR HALOGEN ATOM OR AN ALKYL, ARALKYL, ARYL OR ALKOXY GROUP.

United States Patent C) 3,565,632 HARDENING F GELATIN Peter Richard Mills, Leeds, and Brian Ronald David Whitear, John Peter Stonham, and Anthony Paul Way, Ilford, Essex, England, assignors to llford Limited, Ilford, Essex, England, a British company No Drawing. Filed Nov. 3, 1967, Ser. No. 680,359 Claims priority, application Great Britain, Nov. 8, 1966, 50,035/ 66 Int. Cl. G03c 1/30 U.S. Cl. 96-111 6 Claims ABSTRACT OF THE DISCLOSURE This application describes a process for the hardening of gelatin layers in photographic materials during the processing thereof which comprises applying to the material prior to or during development thereof a dialdehyde of the following general formula:

(IDHO CHO wherein either R or R is an hydroxy group, the other being a hydrogen or halogen atom or an alkyl, aralkyl, aryl or alkoxy group, R and R are the same or different and are a hydrogen or halogen atom or an alkyl, aralkyl, aryl or alkoxy group.

This invention relates to a process for the hardening of gelatin. It is of particular value in the hardening of gelatin layers in photographic gelatino silver halide emulsions.

In the processing of exposed gelatino silver halide photographic material it is desirable that the gelatin should have a relatively tough surface to prevent it being marked during the processing operations, especially during development. It is possible to include a hardening agent in the gelatin as coated, but most hardening agents continue to harden the gelatin for a considerable length of time. Hence, if the photographic material has been stored for some years the gelatin may have become too hard to be successively processed or, alternatively, if the photographic material is comparatively new when it is to be processed the gelatin may not be sufliciently hard and so become marked badly during processing. To some extent the foregoing difficulty can be overcome by including treatment with a gelatin hardening agent as a step in the processing of the photographic material, e.g. as a preliminary step before development or by including a gelatin hardening agent in the developing composition used. The problem in this technique, however, is to find a suitable gelatin hardening agent for such use because many potentially useful agents are found to be unstable in alkaline conditions especially at the high pH values of developers used in rapid processing procedures.

According to the present invention there is provided aprocess for the hardening of gelatin layers in photographic materials during the processing thereof which comprises ice CHO

CHO

wherein either R or R is a hydroxy group, the other being a hydrogen or halogen atom or an alkyl, aralkyl, aryl or alkoxy group, R and R are the same or different and are a hydrogen or halogen atom or an alkyl, aralkyl, aryl or alkoxy group.

It is preferred to add the dialdehydes of the above formula to the developing solution. The preferred quantity of dialdehyde is from 0.5 to 10 g. per litre of developing solution.

Particularly suitable compounds for use in the invention are 2-hydroxy-5-methylisophthalaldehyde, Z-hydroxy-S- methoxy-isophthalaldehyde and 4-hydroxyisophthalaldehyde.

Dialdehydes of the above defined formula are stable and reactive at the high pHs of most photographic developing solutions.

It has been found that when the gelatin layers of photographic material are hardened using the process of the invention they are hardened sufiiciently to prevent them being damaged during the processing. However, when the gelatin layers of photographic material are hardened by this process sometimes a yellow stain is formed in the layers, which is often undesirable. It has now been discovered that this yellow stain may be removed if the photographic material is treated after the development stage with a solution of a hydroxylamine salt or a hydrazine salt.

Therefore, according to another aspect of the present invention there is provided, in a method of processing exposed gelatino silver halide photographic material which comprises the steps of successively developing, fixing and washing the material, the steps of hardening the gelatin layers of the photographic material either before or during the development thereof by applying to the material a solution of the dialdehyde of the above defined formula and subsequent to the development of the material, applying to the material a solution of a hydroxylamine or hydrazine salt.

The hydroxylamine or hydrazine salt may be applied to the material as a separate solution either immediately after development, fixing or the washing step. However, this means the introduction of another processing step and therefore it is often convenient to include the hydroxylamine or hydrazine salt in the fixing solution. The solution of the hydroxylamine or hydrazine salt when applied to the material after development in the above process not only removes the yellow stain but also removes the hardening of the gelatin. Therefore, unless the hydroxylamine salt solution is applied to the material as an additional step in the processing after the fixing and washing it is preferably to include another hardening agent such as an aluminium salt in either the fixing or washing solution, in order to ensure that the gelatin remains hard during the subsequent processing stages.

The following example will serve to illustrate the invention:

EXAMPLE A strip of a fast iodobromide X-ray film, which had been given a wedge exposure, was developed for 90 seconds at 25 C. in a developer of the following composition:

Potassium sulphite-23 gm.

Sodium sulphite (anhyd)20.5 gm. Hydroquinone-ZS gm. 1-phenyl-4-methy1-3-pyrazolidone0.822 gm. Sodium metaboratel8.5 gm.

Sodium hydroxide-9.3 gm.

Disodium ethylene diamine Tetra-acetic acid2.5 gm.

Potassium bromidegm. 1-phenyl-5-mercaptotetrazole0.02 gm. Acetic acid (glacial)-5 gm. 2-hydroxy-S-methyl-isophthalaldehyde2 gm. Water to 1000 ml.

It was then fixed for 90 seconds at C. in an ammonium thiosulphate fixing bath containing an aluminum salt and washed for 2 minutes. A second strip was developed in an identical developer from which the hardening agent was omitted.

The relative hardness of the two strips is shown by the scratch resistance test.

In this test a loaded stylus is drawn across the swollen emulsion surface and the minimum Weight required to scratch the surface is determined. This test is a development of the procedure described by Parker and ISugden. Photographic Science and Engineering, vol. 7, page 41 (1963).

Gm. Developed without hardener Developed with hardener 100 The hardened strip is however bright yellow, the unexposed region having a density to blue light of 0.85 compared with 0.07 for the unhardened strip.

The loss of yellow colouration by treatment with hydroxylamine or hydrazine salts is illustrated in the following table, in which similar pairs of strips to those already described were first developed and then subjected to the following treatments.

Fog density to blue light This shows that subsequent treatment with a hydrazine or hydroxylamine compound removes the yellow stain from photographic material which has been hardened using the process of the present invention.

What we claim is:

1. A process for the hardening of gelatin layers in photographic materials during the processing thereof which comprises applying to said photographic material prior to or during development thereof a dialdehyde of the following general formula:

CIJHO wherein either R or R is an hydroxy group, the other substituent selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an aryl group, and an alkoxy group and R and R are independently selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an aryl group and an alkoxy group.

2. A process according to claim 1 wherein the dialdehyde of the formula defined in calim 1 is present in the developing solution.

3. A process according to claim 2 wherein from 0.5 to 10 g. per litre of the dialdehyde is present in the developing solution.

4. A process according to claim 1 wherein the dialdehyde is selected from the group consisting of 2-hydroxy- S-methylisophthaldehyde, 2 hydroXy 5 methoxylisophthaldehyde and 4-hydroxyisophthaldehyde.

5. A process according to claim 1 which comprises the additional step of applying to the photographic materials after the development thereof a solution of a hydroxylamine or hydrazine salt.

6. A process according to claim 5 wherein the hydroxylamine or hydrazine salt is present in a fixing solution.

References Cited UNITED STATES PATENTS 2,629,659 2/ 1953 Mueller 961 11 3,102,811 9/1963 Barney 260--117 3,168,400 2/1965 Blackmer 96-56 3,451,817 6/1969 Bard 96-111 NORMAN G. TORCHIN, Primary Examiner J. R. HIGHTOWER, Assistant Examiner 

